In my town there's a shop that sells rocks and crystals etc. They also sell sand dollars for $1. That's right, there's a 1:1 conversion rate between sand dollars and USD.
Interesting. In south FL you can (or could, been a while) hit certain places and find the keyhole variant by the hundreds. Fascinating creature, all those tube feet to move. It's illegal to take them but that didn't stop shops from selling the ones that "washed up" which doesn't really happen.
But for some reason people actually buy them. It's a skeleton of a creature someone scooped up and let bake in the sun for a month. Kinda creepy!
It's quite possible, just not my experience. I've seen a lot of really neat shells and stuff wash up but not sand dollars. So i don't want to suggest people actually do that. But it's certainly easy enough. Probably why it's illegal.
I do suggest, if you get the chance, to check them out live. As i kid i had a few skeletons but seeing them in action was way cooler. It's not super exciting or anything, just kinda neat. Same as another one on that list - the horseshoe crab. I helped one get out of a shallow and it seemed appreciative.. at least as much as an ancient creature can be.
Stingrays are kinda dicks though so keep that in mind.